Final answer:
A metastable isotope is an isotope that decays only when prompted by neutron bombardment. It has a longer half-life compared to other isotopes of the same element, making it partially stable.
Step-by-step explanation:
An isotope that contains more than the usual number of neutrons is referred to as a heavy isotope. Heavy isotopes tend to be unstable, and unstable isotopes are radioactive. A radioactive isotope is an isotope whose nucleus readily decays, giving off subatomic particles and electromagnetic energy.
Metastable isotope refers to an isotope that decays only when prompted by neutron bombardment. It has a longer half-life compared to other isotopes of the same element, making it partially stable. It requires an external stimulus, such as neutron bombardment, to trigger its decay.